A mobile telecommunications transmitter, such as a polar transmitter, may include a polar digital radio frequency power amplifier (RF PA) to amplify a signal prior to transmission. In a polar transmitter, the data to be transmitted is separated into amplitude and phase signals. After separation, the phase signal is applied to a phase modulator, and the amplitude signal is applied to an amplitude modulator, such as a radio frequency digital-to-analog converter (RFDAC).
In operation, the RFDAC may be used to modulate the amplitude signal as well as to control the power that is transmitted. Accordingly, there may be a need for systems and techniques for biasing an RFDAC to improve power control and to optimize RF PA power efficiency over a range of output power.